Controller for electric traction motor

ABSTRACT

A controller (10) for the traction motor of an industrial truck comprises an actuator spool (56) which is axially shiftable by a manual selector member (12) for actuating a plurality of control switches (44,46,48). Detent means (86,78,82,84) hold the spool in forward, reverse or park positions and a return spring (66) urges the spool toward neutral position. The actuator spool (56) is adapted for rotational movement about its axis for automatic release of the detent means and return of the spool to neutral position. A seat occupancy detector (18) is actuated when the driver leaves the seat and imparts rotational movement to the spool which releases the detent means and returns the spool to neutral. The controller is also adapted to provide manual and automatic control of a parking brake (6). When the selector member is in the park position, cam means (184) on the actuator spool actuates a control switch (48) to apply the vehicle brake. When the selector member is in the forward, reverse or neutral position the control switch is operative to release the brake with the driver on the seat; if the driver leaves the seat the spool is rotated and actuates the control switch for applying the parking brake.

TECHNICAL FIELD

This invention relates to controllers for self-propelled vehicles; moreparticularly, it relates to manually operated direction and speedcontrollers for an electric traction motor of a vehicle.

BACKGROUND ART

In the prior art, industrial trucks such as lift trucks have beenprovided with controllers actuated by manually operated selector leversfor placing the electric traction motor in forward or reverse drive orin neutral or park conditions. In general, such prior art devicesutilize rotary cams for actuating a directional control switch, brakecontrol means and speed control means. For example, the Hastings U.S.Pat. No. 3,179,198 discloses a controller for lift trucks with a single,manually operated lever for both direction and speed control. Thiscontroller includes a first cam and cam follower for actuating adirection control switch to either forward or reverse position dependingupon the direction of motion of the manual control lever. It includes anadditional cam and cam follower for controlling the release of thebrakes upon movement of the control lever in either direction. Itincludes another cam, which is driven unidirectionally by the first cam,and has a cam follower which controls the vehicle speed through a seriesof sequentially actuated switches. The Ulinski U.S. Pat. No. 2,267,381also discloses a combined direction and speed controller for an electriclift truck. The controller of this patent uses electrical contactors ofthe drum type.

It is also known in the prior art to provide electric lift trucks withautomatic braking when the operator dismounts or leaves his operatingstation on the vehicle. The Hastings U.S. Pat. No. 3,179,198 discloses abrake system in which the brake is applied when the operator dismountsand removes his foot from a pedal on the floor. A failsafe brake isdescribed in which the brake is spring applied and pressure released.The Guhl et al U.S. Pat. No. 4,004,665 relates to a transmission andparking brake controller. The selector lever covers a range of forwarddrive speeds and reverse drive speeds together with neutral and parkpositions. When the selector lever is placed in park position, by atransverse movement of the lever, the fluid pressure to the brake isvented and the brake is spring applied. This system is manually actuatedand not responsive to the operator dismounting from the vehicle. TheBoyajian U.S. Pat. No. 3,507,350 discloses an electric lift truck withmeans for preventing vehicle drive unless the operator's seat isoccupied. The system of this patent uses a seat switch and relay meansfor disabling the power circuit unless the seat switch is closed and thedrive selector is initially in the neutral position.

A general object of this invention is to provide an improved controllerfor the traction motor of an electric vehicle and to overcome certaindisadvantages of the prior art.

SUMMARY OF THE INVENTION

According to this invention, a controller for a traction motor comprisesan actuator spool with cam means and which is axially shiftable in anactuator housing for actuating a plurality of control elements. Amanually actuable selector member is coupled with the spool for axialmovement thereof for selective actuation of the control elements. Detentmeans coact between the spool and the housing for holding the spool incertain selected positions. Spring means urge the spool toward a neutralaxial position and the selector member is also urged thereby throughsaid linkage toward its neutral position. The detent means may bereleased by applying an axially directed restoring force on the actuatorspool by the selector member.

Automatic release of the detent means is provided by a release meanswhich is actuated by condition responsive means. The conditionresponsive means, such as driver presence detecting means, is operativeunder certain conditions, as in the case of the driver dismounting fromthe seat. This causes release of the detent means and return of thecontrol spool to the neutral position.

The controller of this invention is also adapted to provide manual andautomatic control of a parking brake. The cam means on the actuatorspool is adapted to actuate a control element for the vehicle parkingbrake. When the selector member and spool are placed in the parkposition, the control element is operative to apply the vehicle brake.When the selector member is manually moved to any other position such asforward, reverse or neutral, the control element is actuated and isoperative to release the brake. The detent means will hold the controlspool in the park position until it is manually moved to anotherselector position. When the actuator spool is moved to the forward orthe reverse position, the detent means will hold it in the selectedposition subject to automatic release of the detent means and return ofthe spool to the neutral position automatically under the control of thecondition responsive means. When the detent means is released, the spoolis returned by the spring means to the neutral position and the brakecontrol element is actuated by the cam means on the actuator spool sothat the brake is applied.

According to this invention, the actuator spool is an elongated bodyhaving cam means on the surface defining a pair of axially spacedrecesses separated by a land. Cam followers, which are adapted toactuate control switches, are movably mounted in the housing foractuation by the cam means. Preferably, the spool is cylindrical and therecesses are annular grooves in the spool. The spool is biased toward aneutral position and adapted for movement in one direction to a forwardposition and in the other direction to a reverse position. For thispurpose, the spool is provided with an operating stem with a bias springthereon being disposed between a stop member and a retainer member, bothof which are slidably mounted on the stem. The bias spring urges thestop member and retainer member in opposite directions into engagementwith the housing. To hold the spool in either the forward or reverseposition, the detent means comprises a pair of axially spaced recessesin the spool and a spring-loaded ball which is mounted in the housingfor engagement with the recesses.

A more complete understanding of this invention may be obtained from thedetailed description that follows taken with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram representing the interconnection of thecontroller with other components of a vehicle;

FIG. 2 is a perspective view of a lift truck which incorporates thecontroller of the invention;

FIG. 3 shows a seat occupancy detector;

FIG. 4 is a perspective view showing the controller switches in theswitch support member of the housing;

FIG. 5 is a plan view looking down on the controller housing;

FIG. 6 is an exploded view of the actuator assembly including theactuator support member of the housing;

FIG. 7 is a view taken on lines 7--7 of FIG. 5;

FIG. 8 is a view taken on lines 8--8 of FIG. 5 with the actuator spoolin neutral position;

FIG. 9 is a view taken on lines 9--9 of FIG. 8;

FIG. 10 is a view taken on lines 10--10 of FIG. 8 showing the actuatorspool in the detent-release position;

FIG. 11 is a view similar to FIG. 10 but showing the actuator spool inthe detent position;

FIGS. 12 and 13 show the actuator spool in the forward position;

FIGS. 14 and 15 show the actuator spool in the reverse position; and

FIGS. 16 and 17 show the actuator spool in the park position.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring now to the drawings, there is shown an illustrative embodimentof the invention in a controller for the electric traction motor of anindustrial truck, namely a lift truck. The controller provides bothdirectional and speed control for the traction motor with a manuallyactuable drive selector member and a separate, manually actuableaccelerator pedal. It will be appreciated, as the description proceeds,that the invention may be used in other arrangements and applications.

FIG. 1 is a block diagram representing the interconnection of thecontroller of this invention with other components of the industrialtruck in which it is installed. In general, the truck is provided withan electric traction motor 1 which is energized by a battery 2 under thecontrol of the controller 10 and the motor control circuits 3. The truckis also provided with a hydraulic pump 4 driven by an electric motor 5which, in turn, is controlled in part by the controller 10. The truck isprovided with a parking brake 6 of the failsafe type, i.e. the brake isspring applied and is released by hydraulic pressure from the pump 4.

The controller 10, as shown in FIG. 1, includes a start switch 52 whichis connected in series between the battery 2 and the motor controlcircuits 3. The start switch is actuated by movement of an acceleratorpedal 16; the switch is open with the accelerator pedal in its retractedposition and the switch is closed during an initial increment ofmovement when the accelerator pedal is depressed. A speed control member54 of the inductive type is also coupled with the accelerator pedal 16and a speed control signal is transmitted from the member 54 to themotor control circuits 3. Direction control for the traction motor isprovided by a forward control switch 44 and a reverse control switch 46.The forward and reverse switches 44 and 46 are connected in parallelwith each other and in series with the start switch 52 between thebattery and the motor control circuits 3. Thus, the traction motor 1will be energized through the motor control circuits 3 when the startswitch 52 is closed with either the forward control switch 44 or thereverse control switch 46 closed. The controller 10 also includes abrake control switch 48 which is serially connected between the battery2 and the pump motor 5. Accordingly, when the brake control switch 48 isopen the motor 5 is turned off and the pressure to the brake 6 is cutoff and the brake is applied by the brake spring. When the brake controlswitch 48 is closed the pump motor is turned on and the pressure to thebrake 6 is effective to release the brake. The forward control switch44, reverse control switch 46 and the brake control switch 48 areselectively actuated by a manual selector lever 12 which may be placedin park position, forward position, neutral position or reverseposition. When the selector lever is in the neutral position, asdepicted in FIG. 1, both the forward switch 44 and the reverse switch 46are open and hence, the traction motor is deenergized. When the selectorlever 12 is in the forward position, the forward switch 44 is closed andthe reverse switch 46 is open and hence, the traction motor will beenergized when the start switch 52 is closed. Similarly, when theselector member 12 is in the reverse position, the reverse controlswitch 46 is closed and the forward control switch 44 is open and hencethe motor will be energized when the start switch 52 is closed. When theselector member 12 is in the park position, the forward control switch44 and the reverse control switch 46 are open and the brake controlswitch 48 is open. This deenergizes the traction motor 1 and the pumpmotor 5 and hence the parking brake 6 is applied.

The selective actuation of the forward control switch 44, reversecontrol switch 46 and park control switch 48 is also controlled by acondition responsive detector, namely, a driver's seat occupancydetector 18. The occupancy detector 18 is operative, when the selectorlever 12 is in the neutral position to cause the brake control switch toturn off which causes the parking brake 6 to be applied when the driverdismounts from the seat. Also, the detector 18 is operative, when theselector lever 12 is in either the forward or reverse position, inresponse to the driver dismounting from the seat 132, to cause theforward control switch 44 and the reverse control switch 46 to open anddeenergize the traction motor and to cause the brake control switch 48to open which causes the brake 6 to be applied. The controller 10 willbe described in detail presently along with the interconnection thereofwith the selector lever 12, the accelerator pedal 16 and the seatoccupancy detector 18.

FIG. 2 depicts a lift truck with the controller 10 of this inventioninstalled thereon. As described above, the controller 10 is adapted toprovide directional control for the electric traction motor. For thispurpose, the drive selector lever 12 is coupled with the controller andis mounted on the steering column 14 of the vehicle for operation by thedriver. The controller 10 is also adapted to provide starting and speedcontrol of the traction motor and for this purpose it is coupled withthe accelerator pedal 16. The controller 10 is also adapted to controlthe parking brake in accordance with the state of the seat occupancydetector 18.

As shown in FIG. 5, the controller 10 is mounted on a front panel 22 ofthe lift truck. The controller comprises a housing including an actuatorsupport member 24 and a depending switch support member 26. The actuatorsupport member 24 is a unitary body, a metal casting, having a set ofthree mounting bosses 28 which receive respective mounting bolts 30 forsupporting the controller on the panel 22. The actuator support member24 includes a passage 62 which supports a direction control actuator 34(see FIGS. 7 and 8) and includes a passage 203 which extendsorthogonally to passage 62 and supports a speed control actuator 36 (seeFIG. 7), both of which will be described in detail subsequently.

The support member 26 of the controller housing comprises a rectangularbox 38 and a cover plate 42. A set of control switches are mountedwithin the support member 26, as best shown in FIG. 4. The set includesforward control switch 44, reverse control switch 46, and brake controlswitch 48. The start control switch 52 is mounted on the side wall ofthe switch support member 26. Also, the speed control member 54 ismounted within the support member 26. An electrical connector 40 ismounted in the wall of support member 38 to provide for connection ofthe switches and the speed control member with external circuits. Themanner in which the control switches and the speed control member areactuated by the direction control actuator 34 and the speed controlactuator 36 will be described in detail subsequently.

The direction control actuator 34 will now be described in detail withreference to FIGS. 6 and 8. The direction control actuator comprises acylindrical actuator spool 56 having an operating stem 58 at one end andbeing slidably mounted in a cylindrical passage 62 in the support member24. The operating stem 58 extends through a cylindrical chamber 64 to apoint beyond the end of the support member 24. The actuator spool 56 isbiased toward a reference or neutral position which is shown in FIG. 8.For this purpose, a coil spring 66 is disposed in the chamber 64. A stopwasher 68 is disposed in the chamber 64 over the stem 58 and engages ashoulder 72 at the juncture of the stem and the spool 56. The inner endof the spring 66 is seated against the stop washer 68 and the spring 66is retained at its outer end by a cup-shaped retainer 74. The retainer74 is held in the support member 24 by a snap ring 76. The actuatorspool 56 may be moved in either direction from the neutral position;when it is moved leftwardly (as viewed in FIG. 8) the retainer member 74is moved away from the snap ring 76 and the spring 66 is compressed.When it is moved rightwardly, the stop washer 58 is moved away from theinner end wall of the cavity 64 and the spring 66 is compressed.

The actuator spool 56 is adapted to be moved leftwardly from the neutralposition (shown in FIG. 8) to a first position which is herein calledthe reverse position. It may be moved rightwardly to a second position,herein called the forward position, and to a third position, hereincalled the park position. In order to hold the actuator spool 56 in thereverse, forward and park positions, a detent mechanism is provided. Thedetent mechanism includes a partial annular groove 78 for the reverseposition, a partial annular groove 82 for the forward position and afull annular groove 84 for the park position. The detent mechanism alsoincludes a detent element or ball 86 (see FIGS. 6 and 9) which isdisposed in a transverse passage 88 in the support member 24. The detentball 86 is biased toward engagement with the actuator spool by acompression spring 92 which is held in place by a screw 94.

The detent mechanism is adapted to hold the actuator spool 56 in theforward, reverse or park position against the return force exerted bythe bias spring 66. However, the detent mechanism will be released by arestoring force on the actuator spool which will cause the detent ballto be cammed outwardly against the spring by the lip of the detentgroove in which it is seated. Such a restoring force may be applied bythe manual selector lever 12 through an arrangement which will bedescribed subsequently. The detent mechanism may also be released whenthe actuator spool is in the forward or reverse position by a detentrelease means. The detent release means comprises a cam face 96 at theend of the partial annular groove 78 and a cam face 98 at the end of thepartial annular groove 82. The actuator spool 56 is supported forrotation about its axis in the passage 62 and rotational motion isimparted thereto under certain conditions by the seat condition detectormeans 18 which will be described subsequently. When the spool 56 is in adetent position, i.e. the detent ball 86 is seated in the detent groove82, as shown in FIG. 13, rotation of the spool in a clockwise direction(as viewed from the right hand end in FIG. 13) to a detent-releaseposition will cause the ball to engage the cam face 98 and the ball willride up out of the groove and the bias spring 66 will return the spool56 to the neutral position which is shown in FIGS. 8 and 9. Also, whenthe spool 56 is in the other detent position, i.e. the detent ball 86 isseated in the detent groove 78, as shown in FIG. 15, rotational motionof the spool in a clockwise direction will cause the ball to engage thecam face 96 and be lifted out of the groove. This will allow the biasspring 66 to return the actuator spool to the neutral position. However,when the detent ball 86 is seated in the annular groove 84 of the parkposition, rotation of the actuator spool 56 will not release the detentmeans because the groove extends all the way around the spool. Thedetent means is released in park position only by the restoring forceapplied manually through the selector lever.

The arrangement for positioning the actuator spool will be describedwith reference to FIG. 2. The actuator spool 56 is shifted axially inthe passage 62 to the neutral, reverse, forward or park position by themanual selector lever 12. For this purpose, the lever 12 is connectedwith the upper end of a rod 102 which extends along the steering column14 and has a crank arm 104 connected to its lower end. A shift rod 106extends from the outer end of the crank arm 104 to a bracket 108 on anactuator coupling or plate 112. It is noted that the crank arm 104 isjoined to the shift rod 106 by a ball and socket connector 114 toprovide for universal action therebetween. Similarly, the shift rod 106is connected with the bracket 108 by a ball and socket connector 116.The actuator plate 112 is mounted on the stem 58 by an adaptor 118seated on a squared shank of the stem and held in place by a bolt 112(see FIG. 8). When the selector lever is rotated counterclockwise fromthe neutral position the shift rod 106 pushes the actuator spool 56leftwardly (as viewed in FIG. 8) to the reverse position. When theselector lever is rotated clockwise from the neutral position, the shiftrod 106 pulls the actuator spool rightwardly (as viewed in FIG. 8) tothe forward position and to the park position, successively.

In order to impart rotational motion to the actuator spool 56, theactuator plate 112 is provided with a crank arm 124. The crank arm 124is connected through a ball and socket connector 126 and a push-pull rod128 to the seat condition or occupancy detector 18. The details of theseat occupancy detector 18 will be described presently.

For the purpose of determining whether the driver is properly situatedon the vehicle for operation thereof, the seat condition detector 18 isprovided. As shown in FIG. 3, the seat condition detector coacts withthe seat 132 and is operative to assume one condition when the seat isoccupied and another condition when the seat is unoccupied. The seat 132is pivotally mounted on the vehicle frame by a shaft 134. The shaftextends transversely through the front leg-member 136 at a point belowthe vehicle floorboard 138. The seat 132 is spring biased toward aforward-tilt position by a torsion spring 142 which is disposed aroundthe shaft 134. When the seat is occupied by the driver, the driver'sweight causes the seat to pivot counterclockwise about the shaft 134 sothat the rear leg-member 144 is seated on the vehicle body member 146.The seat is illustrated in this attitude in FIG. 3. The seat conditiondetector comprises a lever 148 which is pivotally mounted at its upperend on the shaft 134. The push-pull rod 128 is connected with the lowerend of the lever 148 by a ball and socket connector 152. The lever 148is yieldably urged or biased toward rotation about the shaft 134 in theclockwise direction by an extension spring 154 connected between thelever and the vehicle body. The rotation of the lever 148 in theclockwise direction is limited by a stop member 156 on the lower part ofthe leg-member 136 of the seat. When the seat 132 is occupied and hencein the position shown in FIG. 3, the lever 148 is pushed by the stopmember 156 in a counterclockwise direction to an extended position. Whenthe lever 148 is in the extended position, the push-pull rod 128 rotatesthe actuator plate 112 in a counterclockwise direction, as viewed fromthe right hand end in FIG. 8 and the spool 56 is placed in its detentposition. When the driver dismounts from the seat 132, the torsionspring 142 causes the seat to tilt forward and hence the stop member 156moves rearwardly. This allows the extension spring 154 to contract androtate the lever 148 in the clockwise direction to its retractedposition. Accordingly, the actuator plate 112 is rotated in acounterclockwise direction, as viewed from the right hand end in FIG. 4,and the spool 56 moves to its detent-release position. It is noted thatthis arrangement provides a lost motion connection between the lever 148and the leg-member 136 of the seat so that the seat may be tilted to anextreme forward position for access to the space beneath the seatwithout interfering with the seat occupancy detector. In summary, whenthe seat 132 is occupied, the detector 18 causes the actuator plate 124to rotate the actuator spool 56 to the detent position. When the seat isunoccupied, the detector 18 causes the actuator plate 122 to rotate theactuator spool to the release position.

The actuator spool 56 includes cam means which are operative to actuatethe forward control switch 44, the reverse control switch 46 and thebrake control switch 48 in a selective manner. For the purpose ofactuating the switches, the cam means on the actuator spool are coupledwith the respective switches 44, 46 and 48 by respective cam followers,namely, forward cam follower 162, reverse cam follower 164, and brakecam follower 166. Each of the cam followers is a piston with an arcuatefollower surface for engagement with the cam means on the actuator spool56. Each cam follower is slidably mounted in a respective passage whichextends from the lower surface of the support member 24 to the passage62 containing the actuator spool 56. The rear end of each of the camfollowers is adapted to abut the switch plungers 168, 172 and 174,respectively, of the switches 44, 46 and 48. The switch plungers arespring loaded within the switch housing and are spring biased to anextended position as indicated in FIG. 4. The spring force imparted bythe switch plungers is sufficient to maintain the respective camfollowers in engagement with the cam means on the actuator spool 56. Theforward control switch 44 and the reverse control switch 48 are normallyclosed switches, i.e. with the respective switch plungers 168 and 172 inthe extended position, the switches are in the on condition. The brakecontrol switch 48 is a normally open switch, i.e. with the switchplunger 174 in the extended position the switch is in the off condition.

The cam means on the actuator spool 56 for selective actuation of theswitches 44, 46 and 48 are comprised of axially spaced hilltops andvalleys with axially extending ramps therebetween. In particular, theactuator spool 56 comprises a first recess in the form of an annulargroove 182 adjacent the left end of the spool (see FIG. 8). A secondrecess in the form of an annular groove 184 is disposed axially thereofwith a land 186 therebetween. A second land 188 is provided on the spoolat the left end thereof and is provided with a seal ring 192. Also, athird land 194 is provided on the spool between the annular groove 184and the annular groove 84. The valleys of the grooves 182 and 184 arejoined with the tops of the lands 188, 186 and 194 by respective axiallyextending ramps so that the profile of an axial section of the actuatorspool constitutes a cam surface for coaction with the cam followers 162,164 and 166. An axially extending flat 196 is provided on the actuatorspool 56 and extends through the valley of the annular groove 184 to apoint adjacent the park detent groove 84 for purposes to be describedbelow.

As described above, the actuator spool 56 is rotated between a detentposition and a detent-release position by the seat occupancy detector18. When the driver leaves the seat of the vehicle, it is desirable toapply the parking brake regardless of the position of the selector lever12. For this purpose, the actuator spool 56, as described above,includes cam means which are effective to actuate the brake controlswitch 48 so that the brake is applied when the driver is off the seat.Consider first the position of the actuator spool 56 with the selectorlever in the forward position and the driver on the seat. As shown inFIG. 11, the actuator spool is in the forward position and the detentball 86 is seated in the forward detent groove 82. With the driver onthe seat, the spool 56 is rotated so that the flat 158 thereon cams thefollower 166 to its downward position which maintains the pump switch 48closed. Accordingly, in this condition, the parking brake is released.When the driver leaves the seat with the selector lever 12 in either theforward position or the reverse position the actuator spool moves to theposition shown in FIG. 10 (the neutral position, shown in FIGS. 8 and9). This obtains because rotation of the actuator spool 56 to thedetent-release position allows the return spring 66 to move the spool tothe neutral position where the detent ball 86 engages the land betweenthe forward detent groove 82 and the reverse detent groove 78. In thisrotative position of the spool (shown in FIG. 10) the cam follower ofthe pump switch 48 is in its upper position and the pump switch isturned off allowing the parking brake to be applied.

The speed control actuator 36 will now be described in detail withreferences to FIGS. 2, 4 and 7. The speed control actuator comprises anactuator plunger 202 which is slidably mounted in a passage 203 in atower 204 in the actuator support member 24. The plunger 202 issupported within the passage by a sleeve 206 and includes an annularflange 208 near its mid-section. The sleeve 206 is retained by aninturned flange on the upper end of the tower 204. A spring 212 isseated at its lower end on the bottom of the passage and at its upperend on the annular flange 208. Thus, the plunger 202 is normally biasedupwardly so that the flange 208 is seated against the lower end of thesleeve 206. A stop sleeve 214 surrounds the lower end of the plunger andlimits the downward motion thereof. The upper end of the plunger 202 isconnected through a push rod 216 to the accelerator pedal 16. The lowerend of the plunger 202 engages the head 218 of a speed control plunger222 of the speed control member 54. The speed control plunger 222 isspring biased toward its extended or upper position and is displaceddownwardly by the downward motion of the actuator plunger 202. The head218 carries an actuator cam 224 which is adapted to close the startswitch 52 during the initial increment of motion of the acceleratorpedal 16. The speed control member 54, of known design, is adapted toproduce a speed control signal for the motor control circuits inaccordance with the extent of displacement of the accelerator pedal.

The operation of the controller will now be described with particularreference to FIGS. 1, 2 and 8 through 17. With the driver in place onthe seat 132, the lift truck may be operated with the selector member 12in the park, forward, neutral or reverse position. With the selectorlever in the neutral position, the actuator spool 56 is in the neutralposition, as shown in FIG. 8 and 9. Thus, the cam followers 162 and 164are seated on the land 186 and the forward control switch 44 and thereverse control switch 46 are turned off. Also, the cam follower 166 isheld in its downward position by the flat 158 and hence pump 4 is turnedon and the parking brake 6 is released. With the pump turned on, thelift functions of the lift truck are operational. If the driverdismounts from the seat, the seat occupancy detector 18 rotates theactuator spool to the detent-release position, as shown in FIG. 10, andthe cam follower 166 moves to its upper position and the pump is turnedoff and the parking brake is applied.

With the driver on the seat 132 and the selector member 12 in theforward position, the actuator spool 56 is in the position shown inFIGS. 12 and 13. The spool is held in this position by the detent ball86 which is seated in the detent groove 82. With the spool in theforward position, the cam follower 164 is seated on the land 186 and thereverse control switch 46 is turned off. In this condition, the camfollower 162 is seated in the valley 182 and the forward control switch44 is turned on. Also, in this condition, the cam follower 166 is seatedon the flat 196 and, with the actuator spool 56 in the detent positionthe pump control switch 48 is turned on and the parking brake isreleased. Thus, the driver may operate the vehicle in the forward modeby depressing the accelerator pedal 16. The first increment of motion ofthe accelerator pedal closes the start switch 52 and energizes thetraction motor. Depression of the accelerator pedal produces a speedsignal from the speed control member 36 according to the extent of pedaldepression. If the driver brings the vehicle to a stop and dismountsfrom the seat, the actuator spool 56 will automatically move to theneutral position. When the driver dismounts, the seat occupancy detector18 rotates the actuator spool 56 to its detent-release position in whichthe detent ball 86 rides out of the detent groove 82. This allows thereturn spring 66 to push the actuator spool 56 leftwardly, as viewed inFIG. 13, until the detent ball 86 is seated between the grooves 82 and78. This positions the actuator spool in neutral, as shown in FIGS. 8and 9, and the traction motor is turned off and the parking brake isapplied. The selector member 12 is also returned to neutral by the forceof the return spring 66 which acts through the spool 56 and the linkageis connected with the selector member.

With the driver situated on the seat 132 and the selector member 12 inthe reverse position, the actuator spool 56 is positioned as shown inFIGS. 14 and 15. In this position, the cam follower 162 is seated on theland 186 and is held in its lower position so that the forward controlswitch 44 is turned off. The cam follower 172 is seated in the valley184 in its upper position and the reverse control switch 46 is turnedon. The cam follower 166 engages the flat 196 and is held in its lowerposition so that the pump control switch 48 is turned on. The actuatorspool 56 is held in the reverse position by the detent ball 86 which isseated in the detent groove 78. With the actuator spool in the reverseposition, as described, the driver may operate the accelerator 16 forspeed control in the same manner as described for the forward mode ofoperation. Also when the vehicle is brought to a stop and the driverdismounts from the seat, the actuator spool 56 will automatically returnto the neutral position in the same manner as described for the forwardmode of operation.

With the driver situated on the seat and the selector member 12 in thepark position, the actuator spool 56 is positioned as shown in FIGS. 16and 17. The cam follower 162 is seated against the land 188 and thus isheld in its lower position with the forward control switch 44 turnedoff. The cam follower 172 is seated against the land 186 and is held inits lower position with the reverse control switch 46 turned off. Thecam follower 166 is seated in the annular groove 184 and is in its upperposition so that the brake control switch 48 is turned off. Thus, thetraction motor is deenergized and the parking brake is applied. In thisposition of the actuator spool 56, the cam follower 166 remains in itsupper position with the brake control switch turned off regardless ofwhether the spool 56 is in the detent position or the detent-releaseposition, as determined by the seat occupancy detector 18.

Although the description of this invention has been given with referenceto a particular embodiment, it is not to be construed in the limitingsense. Many variations and modifications will now occur to those skilledin the art. For a definition of the invention, reference is made to theappended claims.

What is claimed is:
 1. A controller for use in a vehicle having anelectric traction motor with forward and reverse drive means,acontroller housing, control means adapted to be actuated for selectingforward and reverse drive, an actuator spool mounted in said housing andadapted for axial movement to neutral, forward and reverse positions,cam means on said spool for selectively actuating said control means, amanually actuable selector member movable to neutral, forward or reversepositions and being operatively coupled with said actuator spool foraxial movement thereof to corresponding positions for selectiveactuation of the control means by said cam means, detent means coactingbetween said spool and said housing for holding said spool in saidforward or reverse position, bias means continuously urging said spooltoward said neutral position, release means for releasing said detentmeans whereby said spool and said selector member are returned to saidneutral position by said bias means, and condition responsive means foractuating said release means.
 2. The invention as defined in claim 1wherein,said vehicle has a parking brake and wherein said actuator spoolis axially movable to a park position and said manually actuableselector is movable to a park position, a control element adapted to beactuated for applying said brake, said cam means coacting with saidcontrol element to apply said brake when the drive selector member is inthe park position.
 3. The invention as defined in claim 2 wherein,saidcam means coacts with said control element to apply said brake when saidselector member is in the neutral position and said condition responsivemember actuates said release means.
 4. The invention as defined in claim2 wherein,said detent means also coacts between said spool and saidhousing for holding said spool in said park position, said detent meansbeing effective to hold said spool in said park position regardless ofthe actuation of the release means.
 5. The invention as defined in claim1 wherein,said vehicle includes a driver's station, said conditionresponsive means includes a detector member adapted for movement whenthe driver of the vehicle dismounts from the driver's station, saiddetector member being coupled with said release means for actuationthereof when the driver dismounts from said station.
 6. A controller foruse in a vehicle having a motor with forward and reverse drive means anda parking brake,an actuator member supported for movement to neutral,forward or reverse positions, first and second control elements adaptedto be selectively actuated by said actuator member for selecting forwardor reverse drive when the actuator member is in said forward or reverseposition, holding means for holding said actuator member in said forwardor reverse position, restoring means for moving said actuator member tosaid neutral position, condition responsive means coupled with theholding means for releasing it in response to a predetermined condition,a driver's station to be occupied by the driver during vehicleoperation, said condition responsive means comprising a detector memberadapted for movement when the driver dismounts from the driver'sstation, said detector member being coupled with said actuator memberfor releasing the holding means whereby the restoring means moves theactuator member to said neutral position when the driver dismounts fromsaid station, said actuator member being supported for movement to apark position, and a third control element adapted to be actuated bysaid actuator member for applying said parking brake when said actuatormember is in said park position.
 7. The invention as defined in claim 6wherein,said actuator member coacts with said third control element toapply said parking brake when said actuator member is in the neutralposition and said actuator is released by said holding means in responseto the driver dismounting from said station.
 8. The invention as definedin claim 1 wherein,said actuator spool comprises an operating stem atone end thereof extending through a chamber in said housing, said biasmeans comprising a stop member slidably mounted on said stem anddisposed in said chamber and adapted to engage the housing at one end ofsaid chamber, a retainer member slidably mounted on said stem at theouter end thereof and being adapted to engage said housing at the otherend of said chamber, a spring disposed between said stop member and saidretainer member, whereby said actuator spool is biased by said springtoward said neutral position and is adapted for movement in eitherdirection from the neutral position against the resistance of saidspring.